Epoxy curing agents are used to cure thiol-terminated sulfur-containing polymers such as polythioethers and polysulfides. Examples of such systems are disclosed in U.S. Publication Nos. 2005/0010003, 2006/0270796, 2007/0287810, 2009/0326167, and 2010/036063. These systems are useful as sealants and can meet the demanding performance requirements of the aerospace industry.
It is desirable that the weight of components used in aviation vehicles be reduced, when possible. As sealants are used throughout an aviation vehicle, a significant decrease in weight can be realized by using low-density sealants. It is well known that the weight of a sealant, coating, or other composition can be reduced by the introduction of low-density fillers. However, the inclusion of additional fillers in a polymeric composition can reduce, disrupt, and/or otherwise affect the network of the cured polymer such that the performance of the cured composition is compromised, especially upon exposure to fuel. For example, in certain epoxy-cured sulfur-containing polymer compositions, the addition of low-density fillers can reduce the elongation of the cured composition.